This invention relates generally to injection fill ports used with tissue expander systems and similar inflatable medical devices. Particularly, this invention relates to an improved injection port structure wherein a magnetic material is incorporated in an injection port assembly. The magnetic material is positioned so that the injection port can be easily and accurately located by noninvasive means. The magnetic material is positioned in the port structure so that it does not interfere with the use of a hypodermic needle for filling purposes.
A tissue expander or similar inflatable medical device is typically implanted under a patient""s skin. In order to expand the tissue structure, fluid is injected using a hypodermic needle or similar device by filling an injection port which is in communication with the tissue expander. As far as is known, the prior art has not proposed or developed a structure which incorporates a magnet with an injection port so that the magnet does not interfere with the injection of a hypodermic needle as does the present invention. For example, in the prior art, U.S. Pat. No. 4,685,447 teaches using a metal plate and X-ray procedure to find an injection port of an implanted tissue expander system, thus exposing a patient to radiation. U.S. Pat. No. 4,671,255 describes a tissue expander system that incorporates a magnet or magnetically detectable material into the injection port by mounting the magnetic material in a recess of the needle guard assembly. The needle guard and/or magnetic material has the propensity to obstruct the end of a hypodermic needle which is injected into the injection port. The latter patent also teaches the use of an inverted hemispheric member to achieve a self-sealing injection port, which complicates the injection port assembly. The present invention overcomes these shortcomings of the prior art by incorporating several structural improvements.
The present invention incorporates a magnet or magnetically detectable material into an injection port of a tissue expander system or into an inflatable medical device for port detection by an external detection means that is constructed and arranged to sense magnetic fields. The magnetic material or element which generates a magnetic field is permanently affixed in the injection port so that its location can be accurately determined by non-invasive external means, thus providing the user with a rapid, convenient, and precise means for locating the injection port. Further, the magnet material is incorporated in the structure which does not interfere with the needle used for filling the tissue expander system.
An object of the present invention is to provide the magnetic material in the injection port but outside of the injection port cavity so that the magnetic material does not obstruct the end of a needle while injecting fluid into the port. Another object of this invention is to completely enclose the magnetic material in a polymer to protect it from environmental exposure. Another object of this invention is to use magnetic material that has been surface treated to prevent the magnetic material from corroding. Yet another objective of this invention is to develop an injection port that is simple in design and easy to manufacture.
This invention provides a magnetic injection port for use with a tissue expander or an inflatable device for implantation. An injection port is used in communication with a tissue expander to permit the tissue expander to be filled with fluid. The tissue expander and injection port are located under the skin and must be properly located in order to permit the filling or inflation of the tissue expander.
The invention incorporates a magnet or magnetically detectable material into the injection port of a tissue expander system or similar inflatable medical device for port detection by an external detection means that is constructed and arranged to sense magnetic fields. The injection port has a body defining a cavity into which the end of a hypodermic needle or similar device is inserted to inject fluid into the cavity. When a desired volume of fluid has been injected into the cavity, fluid flows under pressure via a means of fluid communication, the only means of egress from the cavity, from the injection port into the tissue expander or other medical device. The region of the injection port body into which the needle is inserted is self-sealing to such punctures.
A needle guard member is positioned spacially from and on the opposite side of the injection port body from where the needle enters, to prevent the needle from puncturing the injection port and entering into the tissue expander of the patient. A magnetic material is affixed in the injection port body outside the injection port cavity and the needle guard member. The magnetic material is positioned outside the injection port cavity so that its placement does not interfere with the normal and proper insertion of a needle into the injection port cavity. The magnetic material may be any shape or dimension, and made of any magnetically detectable material. For example, the magnetic material may include samarium cobalt or neodymium iron boron, a combination thereof or like material. The outermost perimeter of the magnetic material is spatially aligned with or within the perimeter of the region of the injection port into which the needle is injected, thus demarcating this region as a target for the needle. The magnetic material also has a surface treatment to prevent it from corroding, such as a nickel coating or the like, and is completely enclosed in a polymer, such as a silicone elastomer or the like, to protect it from environmental exposure.
To locate the injection port, a magnetic detection means is scanned across the region of skin containing the system to establish at least four points of reference creating a coordinate system. The location for inserting the needle is at the intersection of two line segments, each defined by a pair of the reference points established by two passes of the detection means. This intersection is where the magnetic injection port is located and where the medical procedure should be performed.